What do you do? 'who do you work for' or 'what line of work are you in?' These are pretty common questions at most meet and greet or networking type events. They are as much a question about job as they are around identity - where do you fit into the world, how is it similar to what I do and my world, who do we know that might be the same – trying to find commonality and connection.
Initially my response to a question like this was something along the lines of 'oh, I work